selftests: kvm: provide common function to enable eVMCS

There are two tests already enabling eVMCS and a third is coming.
Add a function that enables the capability and tests the result.
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>

tools/testing/selftests/kvm/include/evmcs.h

@@ -220,6 +220,8 @@ struct hv_enlightened_vmcs {
 struct hv_enlightened_vmcs *current_evmcs;
 struct hv_vp_assist_page *current_vp_assist;
 
+int vcpu_enable_evmcs(struct kvm_vm *vm, int vcpu_id);
+
 static inline int enable_vp_assist(uint64_t vp_assist_pa, void *vp_assist)
 {
 	u64 val = (vp_assist_pa & HV_X64_MSR_VP_ASSIST_PAGE_ADDRESS_MASK) |

tools/testing/selftests/kvm/lib/x86_64/vmx.c

@@ -12,6 +12,26 @@
 
 bool enable_evmcs;
 
+int vcpu_enable_evmcs(struct kvm_vm *vm, int vcpu_id)
+{
+	uint16_t evmcs_ver;
+
+	struct kvm_enable_cap enable_evmcs_cap = {
+		.cap = KVM_CAP_HYPERV_ENLIGHTENED_VMCS,
+		 .args[0] = (unsigned long)&evmcs_ver
+	};
+
+	vcpu_ioctl(vm, vcpu_id, KVM_ENABLE_CAP, &enable_evmcs_cap);
+
+	/* KVM should return supported EVMCS version range */
+	TEST_ASSERT(((evmcs_ver >> 8) >= (evmcs_ver & 0xff)) &&
+		    (evmcs_ver & 0xff) > 0,
+		    "Incorrect EVMCS version range: %x:%x\n",
+		    evmcs_ver & 0xff, evmcs_ver >> 8);
+
+	return evmcs_ver;
+}
+
 /* Allocate memory regions for nested VMX tests.
  *
  * Input Args:

tools/testing/selftests/kvm/x86_64/evmcs_test.c

@@ -79,11 +79,6 @@ int main(int argc, char *argv[])
 	struct kvm_x86_state *state;
 	struct ucall uc;
 	int stage;
-	uint16_t evmcs_ver;
-	struct kvm_enable_cap enable_evmcs_cap = {
-		.cap = KVM_CAP_HYPERV_ENLIGHTENED_VMCS,
-		 .args[0] = (unsigned long)&evmcs_ver
-	};
 
 	/* Create VM */
 	vm = vm_create_default(VCPU_ID, 0, guest_code);
@@ -96,13 +91,7 @@ int main(int argc, char *argv[])
 		exit(KSFT_SKIP);
 	}
 
-	vcpu_ioctl(vm, VCPU_ID, KVM_ENABLE_CAP, &enable_evmcs_cap);
-
-	/* KVM should return supported EVMCS version range */
-	TEST_ASSERT(((evmcs_ver >> 8) >= (evmcs_ver & 0xff)) &&
-		    (evmcs_ver & 0xff) > 0,
-		    "Incorrect EVMCS version range: %x:%x\n",
-		    evmcs_ver & 0xff, evmcs_ver >> 8);
+	vcpu_enable_evmcs(vm, VCPU_ID);
 
 	run = vcpu_state(vm, VCPU_ID);
 
@@ -146,7 +135,7 @@ int main(int argc, char *argv[])
 		kvm_vm_restart(vm, O_RDWR);
 		vm_vcpu_add(vm, VCPU_ID);
 		vcpu_set_cpuid(vm, VCPU_ID, kvm_get_supported_cpuid());
-		vcpu_ioctl(vm, VCPU_ID, KVM_ENABLE_CAP, &enable_evmcs_cap);
+		vcpu_enable_evmcs(vm, VCPU_ID);
 		vcpu_load_state(vm, VCPU_ID, state);
 		run = vcpu_state(vm, VCPU_ID);
 		free(state);

tools/testing/selftests/kvm/x86_64/hyperv_cpuid.c

@@ -18,6 +18,7 @@
 #include "test_util.h"
 #include "kvm_util.h"
 #include "processor.h"
+#include "vmx.h"
 
 #define VCPU_ID 0
 
@@ -106,12 +107,7 @@ int main(int argc, char *argv[])
 {
 	struct kvm_vm *vm;
 	int rv;
-	uint16_t evmcs_ver;
 	struct kvm_cpuid2 *hv_cpuid_entries;
-	struct kvm_enable_cap enable_evmcs_cap = {
-		.cap = KVM_CAP_HYPERV_ENLIGHTENED_VMCS,
-		 .args[0] = (unsigned long)&evmcs_ver
-	};
 
 	/* Tell stdout not to buffer its content */
 	setbuf(stdout, NULL);
@@ -136,14 +132,14 @@ int main(int argc, char *argv[])
 
 	free(hv_cpuid_entries);
 
-	rv = _vcpu_ioctl(vm, VCPU_ID, KVM_ENABLE_CAP, &enable_evmcs_cap);
-
-	if (rv) {
+	if (!kvm_check_cap(KVM_CAP_HYPERV_ENLIGHTENED_VMCS)) {
 		fprintf(stderr,
 			"Enlightened VMCS is unsupported, skip related test\n");
 		goto vm_free;
 	}
 
+	vcpu_enable_evmcs(vm, VCPU_ID);
+
 	hv_cpuid_entries = kvm_get_supported_hv_cpuid(vm);
 	if (!hv_cpuid_entries)
 		return 1;